Ok, so I thought I had Marsilea quadrifoliain my 55G for over a year and half. However today, while trying to help another member I was looking at Marsilea quadrifolia pictures and now I'm not sure it's what I have.
This is what is in my tank, and also comes up when searching for Marsilea quadrifolia :
But an image search for Marsilea quadrifolia shows more images of this:
They look totally different to me, the plant in my tank difinitely does not have 4 clovers. Marsilea quadrifolia is described as a clover plant, and I'm pretty sure now that the bottom picture is the true Marsilea. So what is the top picture then?